The present invention relates generally to apparatus and methods for deliquifying solids, for example, swarf generated by industrial machining operations and particularly relates to apparatus and methods for reducing the liquid content of solid particles to levels environmentally acceptable for disposal, for example, in landfills.
While an exemplary embodiment of the present invention, as disclosed herein, refers to the deliquification of swarf in industrial machining operations, it will be appreciated that the present roller/squeezer deliquifier has application to other environments where deliquification of particulate material is desired. The present invention, however, is described herein in connection with its exemplary embodiment, i.e., deliquifying swarf in industrial machining operations.
In industrial machining operations, such as metal cutting or grinding, a liquid is typically provided for the machine tools for purposes of cooling, lubricating, affording enhanced cutting qualities and preventing rust. This liquid, more generally known as a coolant, is typically comprised of a mineral seal oil or a water-based fluid with a soluble oil emulsion or a straight synthetic, i.e., water with a chemical additive. The coolant is circulated to individual workstations, e.g., machine tools, grinders, etc. At the workstations, the coolant serves also to flush the machining waste from the work station for flow to a filtration apparatus, typically a filtration tank common to all of the workstations. It will be appreciated that the coolant, when mixed with the machining waste, has a relatively high solid particles content. For example, the solid particles may comprise metallic particles of steel or iron from the workpieces, as well as the machine tools, or abraded diamonds or carbides, or silica, for example, from abrasive grinding wheels. Additionally, the coolant and machining waste may contain oils used in conjunction with the maintenance and operation of the machine tools. Consequently, the coolant, dirtied by the machining wastes, oils and other contaminants, forms a slurry which flows from the workstations via sluiceways to the filtration apparatus where the majority of the solid particles are separated from the coolant.
The filtration apparatus, for example, may be of the type employing the filtration tank and ancillary equipment described and illustrated in Reissue Patent No. 32,135, dated May 6, 1986 assigned to Henry Filters, Inc. of Bowling Green, Ohio. In that filtration apparatus, there is provided a tank for receiving the slurry from sluiceways communicating between the individual workstations and the filtration tank. The tank contains one or more filter drums for filtering the coolant and for returning it for reuse at the appropriate machining stations, for further separation, or for disposal. To accomplish that, a suction is drawn on the filter drums. This causes a filter cake to be formed about the external surface of the drums. The suction pump thus draws the liquid through the filter cake and filter media of the drum, e.g., fine wedgewire, into the interior of the drum and pumps the filtered coolant from the drum for reuse, further separation or disposal. The drum is indexed periodically to enable a doctor blade to remove the filter cake such that the collected solid particles, principally swarf, of the cake drop to the bottom of the tank. Other, usually heavier, particles settle out to the bottom of the tank without forming part of the filter cake. A dragout conveyor removes these solids from the bottom of the tank.
It will be appreciated that the solid particles lie at the bottom of the tank in contact with the dirty coolant in the tank. Consequently, the solid particles, when withdrawn from the tank, contain a substantial quantity of the liquid coolant. Also, when using a filter drum of the type described and illustrated in Reissue Patent No. 32,135, a cellulosic fiber is oftentimes added to the slurry to improve filtration. Consequently, even additional coolant is retained in the solid particles removed from the tank by virtue of the cellulosic addition to the slurry.
Another type of industrial filtration system employed to filter coolant for return and reuse is described and illustrated in U.S. Pat. No. 4,715,964, also owned by Henry Filters, Inc. In that filtration system, a filter media, for example, a cellulosic paper, is indexed along the bottom of a filtration tank in contact with an underlying screen. The solid particles or swarf collect on the paper media and the clear liquid passes through the paper media into a clean tank for return and reuse to the machining stations, disposal or further separation. The paper filter media is periodically advanced along the bottom of the tank and an inclined ramp at one end of the tank, the paper media carrying with it the solid particles. Similarly as in the filtration system employing the submerged filter drums, the solid particles carried from the filter tank on the paper media have a very high liquid content. It will be appreciated that, while the latter U.S. Pat. No. 4,715,964 illustrates the combination of a filter drum and paper media in a filtration tank, the paper media may be used separately or in conjunction with such filter drum in conjunction with the present invention. It will also be appreciated that other types of filtration apparatus may be employed to separate solid particulate matter from the slurry than those described above and that the roller/squeezer deliquifier hereof may be used in conjunction with such other types of filtration apparatus as well as those described above.
A number of devices have been proposed and constructed in the past to remove the liquid content from the solid particles, mainly swarf, delivered from a filtration tank of the type previously discussed. One device for this purpose is described and illustrated in U.S. Pat. No. 3,980,014, also owned by Henry Filters, Inc. In that disclosure, swarf is disposed through a chute into a briquetting chamber and opposed cylinders at opposite ends of the chamber squeeze the swarf. The chamber is defined in part by walls formed of screen material, for example, wedgewire. While this briquetter has been successful in use, it is susceptible to breakdown when foreign objects are intermingled with the swarf. For example, when the solid particles removed from the filtration tank are handled, i.e., placed in tote boxes, for ultimate disposition into the chute of the briquetting device, there is substantial opportunity for large solid objects to intermingle with the solid particles. The briquetting machine, and particularly its wedgewire chamber, is susceptible to damage by such large solid objects. Moreover, this briquetting machine cannot handle the paper filter media used in the filtration system of the type previously described herein and set forth in previously mentioned U.S. Pat. No. 4,715,964. That is, it is desirable to include the paper media of that filtration system with the solid particles in any deliquification process so that they both may be simultaneously deliquified for ultimate disposal. Because the briquetting machine cannot handle the paper media, current methods of deliquifying the solid particles when using a system employing paper filter medium require the particles to be scraped from the paper media before they are disposed in the briquetting machine and deliquified.
Additional prior apparatus for deliquifying solid particles removed from a filtration tank in the machine tool industry have included an auger disposed within a tube formed in part of screening and having a screen placed adjacent one end of the tube. The end screen is spring-loaded such that, while the liquid flows through the screening, the solids egress radially between the end of the tube and the end screen when the latter is backed off the end of the tube.
Another method of deliquifying solid particles of this type is to form a slug of the material using very high pressure. In most industrial environments, this is not particularly practical. Consequently, there has developed a need for simple economical deliquifying apparatus and methods which will remove the liquid content of solid particles to a percentage of liquid acceptable for disposal.